The present invention relates in general to the design of socket-driven components, typically threaded, which are used in mechanical assemblies to close containers and to attach and secure components in position. More specifically, the present invention relates to the head design for such socket-driven components whereby the component is made one directional when it is to be advanced or removed by means of some hand tool or instrument. The present invention may be incorporated as part of a threaded fastener, a threaded plug, or a threaded lid. Alternatively, the present invention may be incorporated as part of a component which is not threaded, such as a component with a quarter-turn bayonet retaining mechanism. When threaded, the threads may be internal or external in any of the described applications.
Conventional threaded fasteners include a generally cylindrical threaded body and an integral head at one end of the threaded body. There are numerous options for the thread design, including variations in the thread sizes, pitch, and shape. As for the head design, the conventional styles for screws are slotted and cross-recessed or Phillips. Bolts are typically stylized with a hex head or an Allen-socket design. The hand tools used to tighten and/or remove these threaded fasteners are dictated by the particular head design. A screwdriver of either a flat blade or Phillips style is typically used for advancing and removing screws, while a drive socket or wrench is typically used for hex head bolts. An Allen wrench is typically used for an Allen-socket design.
As will be understood, each of the four typical styles of threaded fasteners are intended to be advanced in a clockwise tightening direction as well as removed in a counterclockwise loosening direction. Accordingly, the head designs and the corresponding hand tools for those head designs are configured so as to turn the threaded fasteners in both clockwise as well as counterclockwise directions. In this way, a single, common hand tool is used to both install and remove the threaded fastener. When the present invention is incorporated as part of a plug or lid, the same one directional head design concept is used. The installation options and removal options are the same as with a threaded fastener, depending on the specific head design.
It is envisioned that there are particular applications when it will be desired to restrict the rotation of the component or fastener to only one direction, either clockwise or counterclockwise. For example, if it is desired to prevent the removal, by conventional hand tools or instruments, of a fastener which is tightened in place, the head of the fastener can be made one directional according to the present invention. Likewise, if it is desired to limit how tightly a fastener may be installed, it is envisioned that the head of the fastener and a corresponding hand tool would be designed so that the fastener has to be advanced and tightened by hand, without the use of a conventional hand tool or instrument. The hand tool is then used only for removal, i.e., a one directional design.
According to the present invention, a threaded component, such as a fastener, plug or lid is designed with a head style that is one directional and able to be turned by a square socket drive. In one configuration, this one direction is the clockwise direction for advancing and tightening the fastener, for example, by use of the square socket drive. With this design configuration, the fastener is not able to be removed by a conventional hand tool. In the other primary configuration of the present invention, the one directional fastener head is configured for counterclockwise movement for loosening and removing the fastener. With this design, the fastener would typically be advanced and tightened in place by hand, as conventional hand tools would not be effective due to the special head design according to the present invention. In the counterclockwise design, the threaded fastener may also be advanced and tightened in place by a limited purpose, special instrument which would not typically be available to individuals and personnel who may be in a position to loosen or remove the threaded fastener. This would allow the threaded fastener to be installed and tightened to the degree that it could not be removed manually. With the special head design according to the present invention, the square socket drive would then be the means to remove the threaded fastener by rotating the fastener in a counterclockwise direction. However, the square socket drive would not be effective to threadedly advance the threaded fastener. Consequently, once the threaded fastener was tightened to the desired degree, by use of a special instrument, it could not be tightened to any greater degree by the square socket drive, thereby ensuring that the initially set torque on the threaded fastener would not be exceeded.
One specific application for the present invention is to incorporate the modified head design into a lid which is used on a filter canister. While the lid is intended to be and actually can be easily installed manually, there is a rubber O-ring seal between the lid and filter canister which expands during use. This O-ring expansion causes a tighter engagement between the lid and filter canister making it difficult to manually remove the lid. With the modified head design of the present invention, a square socket drive can be used to remove the lid. The use of a square socket drive imparts greater torque on the lid, enabling the lid to be unscrewed from the canister.
Over the years threaded fasteners have been designed with modified heads in an effort to limit or restrict the direction of rotation of the corresponding fastener. The following listing of United States patents, foreign patents, and foreign applications provides a representative sampling of these earlier design efforts:
______________________________________ U.S. PATENT REFERENCES U.S. Pat. No. PATENTEE ISSUE DATE ______________________________________ 1,506,500 Ripamonti et al. Aug. 26, 1924 3,161,450 Goodenough Dec. 15, 1964 3,253,625 Oestereicher May 31, 1966 3,673,912 Herr Jul. 4, 1972 ______________________________________ FOREIGN PATENT REFERENCES REFERENCE NO. COUNTRY DATE ______________________________________ 1 420 092 Great Britain Jan. 7, 1976 2 036 907 A United Kingdom Jul. 2, 1980 2 149 872 A United Kingdom Jun. 19, 1985 0 584 118 Soviet Union Dec. 1, 1977 (SU 197712) ______________________________________
In several of the designs disclosed by the foregoing list of references, a modified socket shape is provided. Generally, the recessed shape has a series of driving walls and an alternating series of releasing walls. The releasing walls prevent the unauthorized removal of the threaded fastener, see for example U.K. application No. 2 149 872. In other designs, two raised portions are provided to enable conventional advancing but removal only by means of a special tool, see the Herr patent.
Even with these various earlier designs, no one has yet created a head design for a threaded fastener which is one directional in nature and able to be advanced (in one style) or removed (in an alternative style) by means of a square socket drive. This particular combination is provided by the present invention.
The use of a square socket drive provides a number of advantages over other one directional head designs for threaded fasteners. The head design of the present invention provides four, spaced-apart flat walls for use with a square socket drive for either driving advancement or removal, thereby creating a more balanced and more evenly distributed load on the head of the fastener. A square socket drive represents a conventional and readily available hand tool, thereby precluding the need for custom designed or non-conventional hand tools. Accordingly, the present invention represents a novel and unobvious design.